Red curry is much more dry spicy, usually along the red chilies and cilantro flavors. Yellow curry is a sweet-spicy, usually along the turmeric and lemongrass flavors, low notes of ginger sometimes. Neither is usually to be hot-spicy. (Unless you add lots of cayenne pepper or habanero pepper oil, mwhaha, yehiss.) At least to me, however, my tolerance for spicy-hot food has been called unearthly.